Since Fall of 1993, when we completed the manuscript of our book "Semi-
conductor-Laser Physics" [W.W. Chow, S.W. Koch, and M. Sargent III
(Springer, Berlin, Heidelberg, 1994)] many new and exciting
developments have taken place in the world of semiconductor lasers.
Novel laser and ampli- fier structures were developed, and others, for
example, the VCSEL (vertical cavity surface emitting laser) and
monolithic MOPA (master oscillator power amplifier), made the transition
from research and development to production. When investigating some of
these systems, we discovered instances when de- vice performance, and
thus design depend critically on details of the gain medium properties,
e.g., spectral shape and carrier density dependence of the gain and
refractive index. New material systems were also introduced, with
optical emission wave- lengths spanning from the mid-infrared to the
ultraviolet. Particularly note- worthy are laser and light-emitting
diodes based on the wide-bandgap group-III nitride and II VI compounds.
These devices emit in the visible to ultra-violet wavelength range,
which is important for the wide variety of optoelectronic applications.
While these novel semiconductor-laser materi- als show many similarities
with the more conventional near-infrared systems, they also possess
rather different material parameter combinations. These dif- ferences
appear as band structure modifications and as increased importance of
Coulomb effects, such that, e.g., excitonic signatures resulting from
the at- tractive electron-hole interaction are generally significantly
more prominent in the wide bandgap systems.
